The Tuned-Port TradeRecently I scored an '86 Pontiac Trans Am for 400 bucks. The body and interior are in excellent shape, but the car has no motor or trans. I also scored a complete Tuned-Port Injection system for $25, a 700-R4 trans for $200, and a '78 four-bolt 350 for free. My question is: Does anyone make an intake for the Tuned-Port system that will bolt to Vortec heads? If not, will the system work with the '78 heads? Also, I was wondering if there was anything I overlooked with this project? I know that I will need a new fuel pump, bigger injectors, and a chip for a 350 TPI (my car originally had a 305 TPI engine). I'm planning to go with 10:1 compression and a cam designed to work with the TPI system. Oh, and if I do have to use the '78 heads, who makes a set of headers that would work with this setup? Could I use any set made for a small-block Chevy, or would I still need to get a set of headers for the original setup?Eric BanksIsom, KY
Sounds like you've gathered all the makings for a decent street car on an absurdly low budget-nice going. First, there is a lower intake manifold that will allow the use of a TPI induction system with Vortec heads. It's offered by Scoggin-Dickey in Texas, and uses stock-type runners and upper plenum. However, if you did want to use the TPI with those '78 heads, that would be a bolt-on so long as the TPI lower intake manifold you have is one of the earlier castings. In the mid-'80s, the center four bolts of the intake manifold on small-block Chevys were angled differently than the other bolts. These are the bolts that surround the exhaust crossover passage in the intake that would normally pass underneath the carburetor's plenum. The change didn't occur at the same time on all engines, so it can be tough to pin down, especially when dealing with used parts from unknown vintage cars. For TPI-equipped F-cars, the altered bolt angles first appeared for the '87 model year, while Corvettes with aluminum heads got the altered angles a little earlier (sometime during the '86 model year, when the aluminum heads were introduced). Obviously, your '78 heads will have the original-style symmetrical bolt angles, so you need an early-style TPI base. If you find that you have the wrong one, it may be possible to make it work with some creative grinding.
As for your fuel pump, if the stock 5.0L TPI unit is functioning properly, it will be acceptable for the 5.7 TPI system you plan to use. The factory used the same pump for both 5.0 and 5.7 applications, though TPI tuners often prefer to use a higher output pump for performance applications. Jay Fisher of Jay Fisher Pontiac/GMC favors the GMC Typhoon pumps in TPI cars since it's a bolt-in swap that boosts output from the stock pump's 198 liters per hour (lph) rating to about 250 lph.
The injectors are larger for 350 cars, rated at 22 lb/hr while the 305 cars use 19-lb/hr units. The computer and its harness for the 305 can be retained, so long as the chip is programmed for the 5.7L application, and the injectors are spec'd for the larger engine. Going with 10:1 compression for this combination with iron heads is probably pushing it on average pump gas. Since this system uses knock sensors, even mild detonation will cause the ECU to pull some timing, costing you power. Stick around 9.5:1; the minor sacrifice in theoretical will be worth it.
For headers, go with a quality set intended for a third-generation F-car. The exhaust flange for the original TPI heads, the '78 castings, or the Vortec units should be the same, so that shouldn't have any bearing on your choice. However, avoid going with typical universal full-length tubes, even if smog checks aren't a concern for you. The third-gen cars have precious little space under the hood, and even less under the car, so even the full-lengths that fit the engine bay will cause you headaches when it comes time to make up an exhaust system. A good set of shorties with matching high-flow Y-pipe can support plenty of power for the type of combination you're planning. Back it up with a big-diameter single-tube after-cat system and the engine will breathe easy, plus you won't be dragging the exhaust over every imperfection on the road. Edelbrock, SLP, and Hedman all offer tubular shorty-style headers and Y-pipes for your car.